Pathophysiology of primary and secondary hemostasis . Fibrinolysis .

1. May 9, 2017 Pathophysiologyofprimary and secondaryhemostasis. Fibrinolysis.

2. The normal physiological response that prevents significant blood loss following vascular injury is called haemostasis.6 Familiarity with haemostasis lays the groundwork for a thorough understanding of the major disease states associated with thrombosis, such as venous thromboembolism (VTE), atherothrombosis (thrombosis triggered by plaque rupture), and cardioembolic stroke. Hemostasis

3. Hemostasis Subendothelial matrix Hemostatic plug Endothelial cell WBC WBC Fibrin RBC Platelets

4. CLOT FORMATION Platelet Red Blood Cell Fibrin

5. Excessive coagulation leads to the formation of a thrombus, potentially obstructing blood flow. This is a common problem, especially in hospitalised or immobilised patients. Venous thromboembolic disease, for example, is a major problem in the European Union, where it causes more than one million events or deaths every year.Excessive bleeding results when certain coagulation factors are lacking, as in patients with haemophilia. Abnormal haemostasis

6. Blood vessel injury triggers the following sequence: The vessel constricts to reduce blood flow Circulating platelets adhere to the vessel wall at the site of trauma Platelet activation and aggregation, coupled with an intricate series of enzymatic reactions involving coagulation proteins, produces fibrin to form a stable haemostatic plug This finely tuned process serves to maintain the integrity of the circulatory system.However, the process can go out of balance, leading to significant morbidity and mortality. Blood vessel injury

7. ADP Aggregation Aggregation Aggregation GpIIb/IIIa GpIIb/IIIa GpIIb/IIIa GpIIb/IIIa GpIIb/IIIa GpIIb/IIIa Adrenaline Adhesion Adhesion vWF Endothelium Exposed Collagen Platelet Activation Pathways (1) COLLAGEN THROMBIN ADP GpIIb/IIIa Platelet GpIb Adrenaline Adhesion

8. TxA2 Fibrinogen Binding Site Platelet Activation Pathways (2) Thrombin ADP Platelet Fibrinogen Platelet Aggregation Herbert. Exp Opin Invest Drugs 1994;3:449-455.

9. Coagulation involves a complex set of protease reactions involving roughly 30 different proteins. The final result of these reactions is to convert fibrinogen, a soluble protein, to insoluble strands of fibrin. Together with platelets, the fibrin strands form a stable blood clot. The coagulation cascade

11. Thrombogenic and antithrombogenic components in the body

12. Palta S et al., Indian J Anaesth, 58:515-523, 2014

13. „cell-based model“ • This model identifies membranes of cell presenting tissue factor )TF) and a surface of platelets as places of activation of specific coagulation factors. • The model supposes the model of zhree phases: initiation, amplificatopn (propagation) and the proper action of thrombin- thrombus formation. • Initiation = formation of complex TF-FVIIa which is leading to avtivation of a small amount of thrombin. • Propagation = activation of platelets by thrombin and formation of complex FIXa-FVIIIa with subsequent activation of factor Xa. • Thrombus formation = formation of prothrombinase complex anf of large amount of thrombin which is leading to formation of thrombus.

15. Iniciationphaseofcoagulation Palta S et al., Indian J Anaesth, 58:515-523, 2014

16. Coagulation cascade is activated when defect of vessel wall enables contact of the blood with cells with TF. Platelets membrane bound tissue factor TF activates FVII to VIIa which is leding to formation of complex TF-VIIa. The complex binding on platelets membranes activates Factor IX(a) and Factor X(a). Factor Xa converts small amount of prothrombin (Faktor II) on trombin (Factor IIa) which can activate Factor V on FVa and Factor VIII on FVIIIa. Initiationphaseofcoagulation

17. Propagationphaseofcoagulation Palta S et al., Indian J Anaesth, 58:515-523, 2014

18. Propagationofcoagulation: central role forFactorXa • Factor Xa together with activated Factor V (Va) as cofactor support coagulation by thrombin formation (Factor IIa ) from prothrombin (Factor II). • Factor Xa is primary pount for propagation of the porcess; one molecule of Factor Xa catalyses formation of about 1,000 molecules of thrombin.

19. Final step: fibrin formation • In the final step, sequence of serin proteinases reactions which lead to formation of blood clot, thrombin will convert soluble fibrinogen to insoluble fibrin. • Thrombin also activates Factor XIII (stabilizing fibrin) which can stabilize clot by crosslinking of fibrin. • Stabilized fibrin is able to retain cellular components (red blood cells, platelets or both).

20. Fibrinolýza

21. Palta S et al., Indian J Anaesth, 58:515-523, 2014

22. Natural inhibitorsofcoagulation • „Tissuefactorplasminogen inhibitor“ –produced by endothelialcellls. Itinhibitscomplex TF-VIIa. • Antithrombin (previously AT III) – bindsactivated vitamin K dependentcoagulationfactors (canbeactivated by heparin whichincreasesitsbindingcapacity) • „Protein Z dependentprotease inhibitor/ protein Z (PZI)“ produced by liver. ItinhibitsFXa in presence PZ and Ca++.

27. Non activated-after their synthesis in liver Posttranslationally modified –vitamin K dependent coagulation factors = serin proteázy Activated –activated serin proteases, other activated factors (Va, VIIIa) Coagulationfactors -state

30. Screening tests • Bleeding time • Platelet count • Prothombin time (PT) • Partial thromboplastin time (PTT) • Thrombin time (TT) • More specific tests TESTS

31. Venous blood Excessive stress and exercise cause changes in blood clotting. and fibrinolysis. Whenever possible, venous samples should be collected without a pressure cuff (to avoid haemoconcentration, increase of fibrinolysis, platelet release, and activation of some clotting factors. To minimize the effect of contact activation plastic or polypropylene, siliconized glass, syringes and containers should be used. Thoroughly mixing the blood with the anticoagulant by inverting the containers several time. The sample should be brought to the laboratory as soon as possible. Labeling the patient sample is very important. Sampling

32. Anticoagulant trisodium citrate 3.2 % in a ratio of 1 : 9. • Time of sample collection is very important factor in the interpretation of results. • Centrifugation and preparation of platelets poor plasma - 4000 rpm in a cooling centrifuge. • P.T & Factor VII  kept at room temperature. • Other assays  at 4oC. • Testing should preferably be completed within 2 hours of the collection. Sampling

33. Time taken for bleeding to cease from a small superficial wound • Affected by • Platelet count and function • Vessel wall • Normal range Ivy’s method: 2-7 min BLEEDING TIME

34. Normal platelet count = 150-400x109lL • A part of complete blood picture (CBC) • Performed by electronic counters or manually (inherent error) PLATELET COUNT

35. Indicates the overall efficiency of extrinsic pathway of blood coagulation (FVII, FII, FV, X) • Normal range: 10-14 sec PROTHROMBIN TIME

36. Causes of prolonged PT • Liver disease • Vit K deficiency (FII, V, VII, IX are Vit k dependent) • Deficiency of factors involved in extrinsic pathway • DIC • Oral anticoagulants PROTHROMBIN TIME

37. Indicates the overall efficiency of intrinsic pathway of blood coagulation (FVIII, FIX, FXI, FXII, FII, FV, X) • Normal range: 30-40 sec PARTIAL THROMBOPLASTIN

38. Causes of prolonged PTT • Deficiency of factors involved in intrinsic pathway (coagulation factors other than FVII) • Liver disease • DIC • Massive transfusion (labile FV, FVIII) • Heparin PARTIAL THROMBOPLASTIN

39. Prolonged PT + normal PTT= extrinsic pathway defect • Prolonged PTT + normal PT= intrinsic pathway defect • Prolonged PT and PTT= common pathway defect or combined factor deficiencies PT & PTT

40. Platelet count below 150x109/L • Causes: • - Congenital • Acquired • failure of production • Increased destruction (ITP) • - Splenic sequestration (hypersplenism) THROMBOCYTOPENIA

41. ITP is immune thrombocytopenia due to formation of antibodies against platelets and BM megakaryocytes. • Clinical picture: spontaneous bleeding purpuric eruptions. • BT: prolonged • Platelet count:thrombocytopenia • PT,PTT: normal • BM:increased megakaryocytes with poor platelet separation Idiopathic Thombocytopenic Purpura

42. Platelet function defect + normal plt count • Causes: • Hereditary (Glanzmann’s disease, Bernard-Soulier syndrome) • Acquired (drugs as aspirin, uremia) QUALITATIVE PLATELET DEFECT

43. Clinical picture: spontaneous bleeding purpuric eruptions. • BT: prolonged • Platelet count: normal or slightly decreased • PT,PTT, TT: normal • Platelet function: abnormal depending on the defect (defective aggregation in Glanzmann’s disease and Bernard-Soulier syndrome) QUALITATIVE PLATELET DEFECT

44. Hereditary thrombofilia AT deficiency Protein C deficiency Protein S deficiency Factor V Leiden Prothrombin polymorphism (G/A 20210 in 3´ area of the gene) HereditaryThrombophilia

45. Syofantiphospholipidantibodies Increasedlevelsoffactors VIII, IX, XI and fibrinogen Fibrinolysisdefects AcquiredThromboticdisorders

48. Heparin • Bleeding • Thrombocytopenia • Osteoporosis • Hypersensitivity Heparin/LMWH—Adverse Effects • LMWH • Bleeding • Thrombocytopenia • Hypersensitivity

49. Fatal or non-fatal hemorrhage from any tissue or organ • Necrosis of skin and other tissues • Other adverse reactions reported less frequently include: • Systemic cholesterol microembolization • Alopecia • Purple toes syndrome, urticaria, dermatitis including bullous eruptions Warfarin—Adverse Effects